The present invention relates to a system of informing procedures for adjusting the control parameters of an electric power steering control apparatus, which applies power to the steering system of an automobile for assisting steering action.
The recent advancements in the automobile technology have resulted in various types of electric components that control actuators based on information from sensors. The electric power steering control apparatus is one such component. A typical electric power steering system includes a torque sensor, which is attached to a steering shaft connected to a steering wheel. The torque sensor detects the steering torque. An electric power steering control apparatus computes an assist command current based on the detected steering torque and a vehicle speed detected by a vehicle speed sensor. Then, the control apparatus controls an electric motor so that the actual motor current, detected by a current sensor, is equal to the computed assist command current, thereby reducing the force required for steering.
The electric power steering control apparatus includes a controller, which is an electronic control unit (ECU), and operates according to a control program and control parameter data, which are stored in a read only memory (ROM) of the controller.
Various control parameter data, which is previously stored in the ECU, is adjusted for each vehicle. This adjustment is referred to as actual vehicle adaptation. The actual vehicle adaptation is performed during the development of a vehicle to adjust the various control parameter data such that the characteristics of the electric power steering control apparatus are adapted to the characteristics of the vehicle. In the actual vehicle adaptation for an electric power steering controller, several items of the steering feeling are determined. The items include the resistance of steering, the behavior of the steering wheel when it returns to the neutral position, the reduction of the vibration of the steering wheel, the response of steering, and the maneuverability of the vehicle. Through the actual vehicle adaptation, the performance of the electric power steering control apparatus and the steering feeling are improved.
In general, an electric power steering control apparatus refers to a great number of control parameters and integrates outputs from several control algorithms to determine a command torque (assist command current), which is sent to an electric motor. Thus, even if one control parameter is determined, the determined parameter must be adjusted after other control parameters are determined. That is, the control parameters influence one another in a complicated manner, which complicates the adaptation procedure.
Also, it is not easy to determine the correspondence between each of various control parameters and the items of the steering feeling. Therefore, the adaptation is performed by try and error and takes long time.
Accordingly, the adaptation requires high skills and experience. That is, the adaptation is a special procedure that can be performed only by skilled workers. Therefore, the adaptation cannot be performed on different types of vehicles at the same time and is not suitable for accelerated development of vehicles.
Accordingly, it is an objective of the present invention to provide a system of informing procedures for adjusting control parameters of an electric power steering control apparatus, which system constructs a database defining the relationship between control parameters and items of steering feeling and informs an operator of which of the control parameters should be adjusted in what manner in order to resolve problems regarding the steering feeling.
To achieve the foregoing and other objectives and in accordance with the purpose of the present invention, an informing apparatus for informing procedures for adjusting control parameters used in a control apparatus that controls an electric power steering apparatus based on various control parameter data is provided. The power steering apparatus is used for the steering wheel of a vehicle. The informing apparatus includes storing means, first input means, second input means, reading means, and output means. The storing data means stores evaluation data, steering state data, control parameter data of the power steering control apparatus, and adjusting procedure data. The evaluation data is related to steering of the steering wheel. The steering state data represents the steering state when the evaluation data is obtained. The steering state data is related to the evaluation data. The control parameter is related to the steering state data and the evaluation data, and is being used when the evaluation data is obtained. The adjusting procedure data is used for adjusting the control parameter data such that the evaluation data is resolved. The first input means inputs the evaluation data. The second input means inputs the steering state data. The reading means reads the adjusting procedure data of the control parameter data from the storage means based on the evaluation data and the steering state data. The output means outputs the adjusting procedure data of the read control parameter data.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.